Summary:Pathological correlations were sought between cerebral amyloid angiopathy (CAA) and other classical neurodegenerative changes in 101 consecutive cases of autopsy- confirmed Alzheimer disease (AD). Some degree of CAA was found in at least one area of the brain in 81% of the cases; severe CAA was found in at least one brain region in 29% of the cases. In a subset of 42 cases for which genomic DNA was available, greater severity of CAA was associated more with cases that were homozygous for apolipoprotein e4 than in cases with only one or no e4 alleles (Fisher's exact test,p= 0.005). In all brain regions, severity of CAA was inversely correlated with numbers of neurons. This correlation was statistically significant in the temporal lobe (r=-0.29,p= 0.004) and the frontal lobe (r=— 0.22,p= 0.02). Our findings suggest that two factors may modify the severity of AD pathology: Apolipoprotein E4 may accentuate the vascular deposition of β-amyloid, and severe CAA may accelerate neuronal loss.